The skin and/or fur of an animal form a barrier to the environment. This barrier being capable of adapting itself to varying environmental conditions. Besides this, the skin and/or fur play an important physiological role in providing physical protection, assisting in the thermal regulation of the organism and providing a metabolic, sensorial and storage function. The physical barrier function of the skin is mainly exerted by the outermost lipid layer or stratum corneum. The ceramides present in the stratum corneum ensure protective properties towards the environment and form a lipid filter limiting evaporation of moisture from and controlling permeation of external substances into the skin.
Besides this physical barrier function, the skin also exerts a chemical barrier function as its surface is colonised by a wide variety of microorganisms that assist in maintaining a natural equilibrium of the skin.
However environmental action and contact of the skin with cleansing or other products may involve distortion of this natural equilibrium, an uncontrollable outgrowth of certain micro-organisms within the skin microflora and the consequential impaired lipid barrier function and dermatologic infections.
It has been found in the recent years that also with animals. in particular furry animals, domestic animals as well as farm animals, the number of cutaneous infections where over-populations of microorganisms intervene is severely increasing. In particular, the occurrence of primitive infections. dermatoses over-infections and parasitoses has been more frequently observed. It is believed that the changing living conditions of the animals, the ensuing occurrence of bacterial and fungal overpopulation and a consequential weakening of the fur, may be possible causes thereof.
In this respect it has for example been observed with animals like cats and dogs that dermatoses and parasitoses induce severe scratching of the animal, which in turn involves alteration of the microbial microflora residing on the fur and skin, inflammatory reactions and keratinisation troubles. The latter are mostly treated through application of antibiotics and anti-inflammatory agents associated in an emollient. These products however have been found to be inconvenient because of their aggressiveness tot he skin and fur and because they do not respect the ecoflora naturally occurring with the animal.
It becomes apparent that malfunctioning of the cutaneous barrier may involve widely varying immunologic reactions with the animal, in particular an augmentation of the microbial and fungal sensitivity, a bacterial proliferation and inflammatory reactions. In particular, with animals like cats and dogs, localised or general keratoseborrheaic phenomena resulting from problems associated with sebum secretion or keratinisation anomalies, constitute a characteristic reaction for furry animals.
The observed increase of the occurrence of primitive infections, dermatoses over-infections and parasitoses thus obviates the need to a composition, suitable for topical application on animal skin and/or fur, the composition being capable of treating these phenomena.
From WO 98/49999 it is known that sphingoid base containing formulations show growth-inhibitory activity against gram-negative as well as against gram-positive bacteria, when present in a concentration of at least 0.005 wt. %. Antimicrobial activity of sphingoid bases has been found against bacteria, yeasts and fungi. Typical applications include treatment of acne, dandruff, mycoses, i.e. cosmetic and/or dermatological applications on skin and hair.
Bibel et al in Clinical and Experimental Dermatology 1995, 20, 395-400 express their doubt about the suitability of sphingosin and sphinganin in clinical uses for their anti-microbial and anti-fungal activity. Formulations containing sphinganin were effective against Candida albicans and Staphylococcus aureus, in test experiments where inflammated, depilated guinea pig skin are used as simulators for human skin. Sphingosin had little effect. However, anti microbial activity against staphylococcus present on human tissue does not necessarily entail activity against specific staphylococci appearing with animals.
DE-A-196 02 108 and DE-A-196 02 111 relate to the use of sphingosin or phytosphingosin based sphingolipids as a deodorant. The object of using sphingosin or phytosphingosin is to obtain deodorant which is capable of selectively fighting those bacteria that are responsible for the unwanted sweat odour with human beings, leaving the normal microbial population and the human temperature regulating system unaffected.
WO95/03028 relates to a skin-renewal-stimulating cosmetic composition for frequent and repeated topical application to normal skin. The composition contains skin-renewal-stimulating acids for improving the appearance and condition of the skin. The long-term irritation induced by topical application these skin-renewal-stimulating acids is reduced through incorporation of a sphingosin material into the formulation.
The above-described applications are mainly limited to the field of cosmetic products, the use of sphingoid bases in veterinary applications not being touched.